1. Field of the Invention:
The present invention relates to an apparatus and a method for expanding an operation region of a power amplifier. More particularly, the present invention relates to an apparatus and a method for expanding an operation region of a supply modulated amplifier for amplifying power of an input signal using a supply voltage modulated with consideration of an amplitude component of an input signal.
2. Description of the Related Art:
With development of wireless communication technology, as the need for transmission of various multimedia signals increases rapidly and fast transmission in a mobile environment becomes necessary, interest in a 4th generation communication system is increasing rapidly.
The 4th generation communication system has a faster transmission speed, a wider bandwidth, and a larger Peak to Average Power Ratio (PAPR) than previous communication systems. Accordingly, the 4th generation communication system uses a supply modulated amplifier that amplifies an input signal using a supply voltage modulated with consideration of an amplitude component of the input signal. For example, the supply modulated amplifier uses an Envelop Elimination and Restoration (EER) amplification method, an Envelope Tracking amplification method, a polar amplification method, etc.
The supply modulated amplifier may obtain a high efficiency as illustrated in FIG. 1 by changing a supply voltage of a power amplifier depending on output power of the power amplifier to reduce power loss.
FIG. 1 illustrates a power amplify efficiency according to the related art.
Referring to FIG. 1, where a power amplifier amplifies power of a signal using a fixed supply voltage 100, a power amplify efficiency rapidly decreases in a high power level region. When a supply modulated amplifier is used in a high power level region 110, the supply modulated amplifier may raise a power amplify efficiency in the high power level region.
In case of using the ET amplify method, the supply modulated amplifier is configured as illustrated in FIG. 2.
FIG. 2 illustrates configuration of a supply modulated amplifier according to the related art.
Referring to FIG. 2, an ET amplify type supply modulated amplifier includes a baseband signal processor 200, an envelope generator 210, a supply modulator 220, a Radio Frequency (RF) processor 230, and a power amplify module 240.
The baseband signal processor 200 generates IQ data. The RF processor 230 converts IQ data provided from the baseband signal processor 200 to an RF signal and provides the same as an input signal of the power amplify module 240. The envelope generator 210 generates an envelope corresponding to IQ data provided from the baseband signal processor 200.
The supply modulator 220 determines a supply voltage of a High Power Amplifier (HPA) 242 forming the power amplify module 240 based on an envelope generated by the envelope generator 210.
The power amplify module 240 includes the HPA 242 for amplifying a signal of a high power level and a Low Power Amplifier (LPA) 244 for amplifying a signal of a low power level. The HPA 242 amplifies an input signal provided from the RF processor 230 using a supply voltage provided from the supply modulator 220 and outputs the amplified input signal. The LPA 244 amplifies an input signal provided from the RF processor 230 using fixed power and outputs the amplified input signal.
As described above, the power modulated amplifier can raise a power amplify efficiency of a high power level signal using the HPA 242 that uses a supply voltage modulated with consideration of an amplitude component of an input signal. However, since the LPA of the supply modulated amplifier uses fixed power, a power amplify efficiency of a low power level may be lowered. Accordingly, in the case where transmission of a low power level signal increases in a transmission terminal, power consumption may increase due to a low power amplify efficiency in the transmission terminal.